The conversion of carbonaceous materials into energy and other products often involves a thermochemical conversion step. In the production of energy, carbonaceous materials may for example be combusted to generate heat.
Alternatively, carbonaceous materials may be converted into other products through thermochemical processing. Examples include the conversion of coal into fuels by means of gasification followed by further chemical reaction of the resultant gas mixture comprising carbon monoxide and hydrogen.
Alternatively coal may be liquefied by heating at high temperature and pressure in the presence of catalysts and a hydrogen-transfer solvent to produce liquid products directly.
Coking coal is produced via the pyrolysis of coal under inert conditions or vacuum to produce essentially three products: a gaseous product, a liquid product (pyrolysis oil), and a solid product (coking coal). The latter process is normally carried out at very high temperatures (>1000° C.). In a variant of the latter process, pyrolysis may be carried out at moderate temperatures (˜600° C.) to produce pyrolysis oil and a partially de-volatilized coal.
Crude oil, on the other hand, is normally subjected to an initial high temperature distillation process in order to separate the oil into different boiling point fractions. Such distillation processes generally generate four crude products, namely a top fraction containing all the lowest boiling components; a middle fraction which contains components with medium boiling points; a heavy fraction (high boiling points); and a bottom fraction that cannot be distilled.
To date there is little that can be done to change the properties of materials such as coal, charcoal and crude oil with the view to improve the thermochemical processing of such materials to provide improved yields or improved product properties. As an example, during the distillation of crude oil, the nature of the crude oil typically determines the relative proportions of the basic products.
Our earlier international patent application publication number WO 2012/025806 discloses that fine coal and other carbonaceous material may conveniently be rendered usable by agglomeration using microalgae biomass as binder for fine carbon particles. This work with microalgae and carbonaceous material has led to further processes being developed as will be further described below.
In this specification the term coal or carbonaceous fines should generally be interpreted to mean sub 250 micron particle sizes. It is however preferred that the particle size actually to be sub 150 micron for the more efficient operation of the invention as will become more apparent from what follows.